In medical navigation, a patient reference or reference array is fixed with respect to a part of the body to be treated. In the area of spinal treatment, for example, this conventionally has been achieved by attaching the reference array to an exposed section of bone and then registering, i.e., positionally assigning, the reference array in a navigation system. A disadvantage of such conventional methods is that in order to gain access to the section of bone (e.g. vertebra) to which the reference array is to be attached, relatively large incisions into the skin and through the tissue must be performed. In cases where the actual surgery can be performed using a thin and/or small instrument, the problem then arises that attaching the reference array represent the most invasive aspect of the entire treatment.
A localizing device for determining the position of a patient is known from DE 102 06 166 A1, wherein a vacuum mattress is used to place the patient. A box-like couch, which includes two side walls that stand up on both sides of the patient, is placed around the vacuum mattress and the patient. Navigational markings are arranged on the sidewalls, and the patient is immobilized and fixed with respect to the markings. A disadvantage of this is approach is that the patient and/or the area to be treated is relatively far from the markings, which can reduce the accuracy of the navigation. Also, the proposed box-like arrangement is very bulky and difficult to handle, and can obstruct the area to be treated.
DE 197 31 040 A1 describes a device and a method for fixing parts of a body, wherein a patient is positioned on a bearing surface and then covered with a foil. The patient is immobilized by suctioning air from under the foil, thereby collapsing the foil around the patient. The reference, as a secondary aspect, also describes how holding arms can be used that include a base beneath the foil, wherein the holding arms pass through the foil and are attached at the other end to the patient couch. The holding arms are designed with joints and are attached both to the patient and to the couch only via the suctioning effect created by the partial vacuum. DE 197 31 040 A1 also proposes attaching a marker system to the holding arms. However, attaching the holding arms via the foil and partial vacuum may not offer a sufficient holding force to rigidly fix such markings with respect to the patient. As a result, accuracy in navigation can be affected. Further, due to the holding arm joints and the unstable fixing by means of the foil, a fixed arrangement of such markings with respect to the parts of the body cannot be ensured.